1. Field of the Invention
The present invention relates to a method for differentiating asbestos materials from aramid materials, and to apparatus for use in performing the method. In particular, the invention relates to a method and apparatus for differentiating asbestos-based friction materials from aramid-based friction materials.
2. Description of the Related Arts
The terms "asbestos material" and "aramid material" are used herein to refer to materials which are comprised wholly or substantially of, respectively, asbestos and aramid.
Traditionally, asbestos has been used in friction materials such as vehicle brake and clutch components because of its toughness and non-flammability. In recent years, however, the use of asbestos in such applications has been restricted in many countries. Instead, an alternative material, aramid, has been increasingly used instead of asbestos. Aramid is a tough, synthetic fibrous material which is believed to be safer to health than asbestos.
Because of the restrictions with asbestos, and because of a worldwide drive to refurbish or recycle automotive components where possible, it is desirable to be able to differentiate asbestos-based materials from aramid-based materials in automotive components, notably in brake or clutch linings. Such differentiation permits disposal of each component in a suitable environmentally-friendly manner. Asbestos is invariably disposed of, but aramid fibre can be recycled.
In a known method of differentiating asbestos from aramid in an automotive component, a sample of the component is crushed into small particles and identified by viewing under a microscope. When viewed in this manner, asbestos fibres look different to aramid fibres, enabling an identification to be made. A problem with this method is that it is slow and cumbersome.
A requirement for any practical industrial method of identifying friction materials for possible recycling is that the identification is made quickly, preferably in less than one minute per sample. Slow identification speeds would slow down the rate at which components could be grouped according to material type, and this can have a significant effect on the economics of any recycling process.